Relay testing apparatus



Dec. 26, 1933. A, D, Down 1,941,253

RELAY TESTI NG APPARATUS Dec. 26, 1933. A. D. Down RELAY TESTINGAPPRATUS 2 Sheets-Sheet F/GZG Filed April 30, 1932 M 7 a S L. M H 7 3 ms7 7 /A/r/E/v To@ A. D DOWD Afro/ mfr Patented Deze, .1933

PATENT oFFl-cs n 1,941,253 RELAY TESTING 'APPARATUS Andrew D.Dcwd,Montclair, N. J., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., acorporation of New YorkV ApplicationApril l3l), 1932., Serial No. 608,364

5 Claims. (Cl. 1775-183) This invention relates to relay testingcircuits,

and more particularly-'to circuits for measuring the efficiency ofrelays.V j` 1 An object of this invention is to provide a simple circuitarrangement for testing of relays.

A further Objectis toprovide a circuit capable of accurately testingrelay efficiency in less time and Vwith greater facility-than.isattendant upon use ofthe circuits heretofore employed. Another object isto'readily `observe by indications on a meter diiierent `operatingcharacteristics of the relay under test. n

' Telegraph relays requiPv frequent tests and adjustments to maintain ahigh efliciency of operation. The followingV tests are usually ,re

quired'z` marking and spacing adjustment, Whichis a test for thepreliminary adjustment of the pole pieces, either to avoid-that the polepieces prevent the armature from 'reaching the con-I tacts, or to avoidthat the armature failto reverse at normal operating current due to thepole pieces being too close to the armature; contact efficiency, toascertain Whetherv the contacts arer clean, Whether the contactsprings'are vequally spaced, or Whether there is a loose connection k inthe Wiring to the contact springs; biasing adjustment, Which is atesttoattain a desired bias, or'an absence of bias; relay position, va test'todetermine Whether the armature is in the marking-'or spacing position. ff In accordance with the invention, a single circuit Yis providedwhichvvill vfacilitate'the frequent performance of these tests, eitherin the shop or in the field. The testing arrangement in accordance withthe invention includes a meter having the Zero point in the center ofthescale, and connected for deiiecting the needle in opposite vdirectionsto a shunt Yresistance having its middle point grounded.v A pluralityofswitching devices serve to modifythey circuit arrange--,

ment for the diierenttests. By means of the double deflection featureofr this'meter, it is possible to assign one direction of deec'tionl tothe marking contact kand 'the other to the spacing contact for any andall of the tests, thereby' greatly facilitating the Work ofadjustingvthe various parts ofthe relay to correct for the errors4 indicated bythe meter. vl .i H s `Before proceeding with the severalvtests, it iscustomary, first, to' examinethe relay forloose parts and to'tightenthem, if any are found.

The vrela-y is Vinserted in atest panel `which Will be consideredAlater. The relay and armature. contacts should then be cleaned offoreign matter. The pole pieces vare then backed off as far as possibleso as'to eliminate any electrical bias, and it. can then be `observedWhether the varmature is poised approximately in thecenter of the hollowcore of the relay. If the armature is not correctly positioned,` it canbe removed keys.

and readjusted so thatvit will assume the center position whenreassembled inv the relay. Thenr the relay contacts 'are` backed off sothat theV armature will not touch the contacts. vWith bat-"1 teryapplied to the armature, one contact is advanced until it just touchesthe armature as will be indicated by the deflection kon the meter. Thiscontact is then backed` off until the disjtance between itand thearmature contact is approximately .002. This operation is repeated Withthe relay contact on the opposite side of f the armature, so thatthereYis-a totalgap` of about ,004. With 20 cycle current then appliedto thefwindings7V the pole pieces shouldbe ad,-y vanced alternatelyuntil theneedlel on the: meter vibrates steadily Vat mid-scale. k f

Referring now to the accompanying drawings: Figfl isadiagrammaticrepresentation of the test circuit inaccordance With apreferrediorrn of thefinvention.

FigsZA, 2B, 2C,

3, 4 and l5 represent in simpli-y fied form .those parts of the circuitshown'in Fig. l Which are effective in various tests in ac-v cordance:ywith Jdifferent manipulations of the `The circuit, Aasillustrated inFig. l, comprises the keys l0, 20 and 50,l Whichare three-positionkeys,.and the tivo-position keys i0 and y50 which will'z bev operated indiierentxmanners forVl the derent circuit combinations recniired forvarious tests. ,The key i0f`or the connection of the batteryl supply-must be` closed for all tests, vand 1 will be assumed to beclosed atall times in the following descriptions. @An alternating current sourceis provided for operation -of the relay undertest at a frequencyapproximating the sig.-

naling frequency. y v f y q ,The meter '70 hasfascale with the Zeropoint Yin the middle and isadapted todeflect in opposite directions asthe current is reversed through its Winding. This meter is usedforobservation in all the tests and the connections are made so thatdeflections toward right and left, respectively, indicateclosure of themarking andnspacing contacts on the test relay. i l

i Inythe preferred form of the invention illustrated vin the drawings,the'testing circuit is especially adapted for accommodation of astandard `type of high speed telegraph relay. *Such relays are generallyassociated With their voper- 'ating circuits by the insertion of fixedprongs on the base of the relay intocorresponding jacks loc in aconnecting block, mounted on the operating v As shown in Fig. 1 thestandard relay 65, which is to be tested, is inserted bymeans of prongsinto a connecting block which has contact springs corresponding to theprongs of the relay serving to connect the relay to the testing circuit.Upon insertion of the relay into block 60, the relay windings will beconnected in series and will remain so for all tests.

The relay for the testing of which the present embodiment or" theinvention is particularly designed is of the type described in Patent1,680,667 to A. M. Curtis, issued August 14, 1928. The armature 64 issurrounded by two stationary operating windings 66 and 6'7 and its freeend swings between two adjustable pole pieces 68 and 69 of a lowcoercivity magnetic system which provides a double return path for theoperating iiuxes produced by the winding; a permanent magnet has itspoles connected to this double magnetic system near the pole piecesthereof to provide a polarized reaction flux; the end of the armaturecarries a damped contacting member cooperating with stationaryadjustable contactpoints M and S, corresponding to the marking andspacing positions of the armature. v

Whereas, Fig. 1 illustrates the complete test circuit, it is believedthat a better understanding of the operation ofthis circuit will bepossible by having reference to the simplied diagrams of Figs. 2 to 5 inconnection with the following descriptions of the individual tests. y

VTest ,for marking and spacing adjustment From' this circuit it willreadily be observed that battery 47 is applied over resistance 45 andseveral contacts in series of the various keys tofthe windings of Arelayand the circuit may be further traced` through the relayA windingsinseries over another group of key contacts to ground. Current flowingin this circuit operates the armature to its spacing contact; resistance'45 is low and the current will be heavier than normal operating currentto insure that the armature operates even should the pole piece onmarking side be too closely adjusted. For a particular type of relaythis soak current is .004 ampere.

After this preliminary operation, key 10 is operated to the left oroperate position and key 20 remains in the marking position,` wherebythe eiective circuit will be changed to that shown in Fig. 2B.

-It will be observed that the battery and ground connections to therelay windings have been `Vreversed.

rlhe current through the windings has been reduced to normal operatingstrength by insertion TheV ing side interferes with the movement of thearmature, preventing it from making the M contact, and adjustment mustbe made until a deiiection is` obtained on the meter.

For the final step in the test, key 20 remains in Ymarking position andkey'lO is rst operated to pass through normal position, therebyreestablishing the circuitshown in Fig. 2A and causing the armature toreturn to spacing position under the influence of the heavy soakcurrent. Key 10 is then moved into non-operate Vposition and theeiective circuit will be as shown in Fig. 2C.

Battery and ground connections to the relay 65 remain the same as inFig. 2B but an additional resistance 52 is now in series with thebattery -pole piece on the spacing side was too great.

The test for spacing adjustment is similarin all respects to the testfor marking adjustment describedl above, excepting that key 20Ywhenoperated is moved to spacing instead of to marking position.

On completion of the test for marking and spacing adjustment keys 10 and20 are restored to normal as in Fig. 1.

Contact eiciency In this test the object is to learn whether thecontacts are eicient and free from dirt.-

., The effective circuit for the contact efficiency test is shown inFig. 3, and is obtained by closing key 40 and operating key 30 to theleftor contact eiiiciency side.

By the operation of key 30 an alternating current source 80 is connectedto the windings or relay 65. ance with the frequency of the 'source 80will oscillate between relaycontacts S and M. Battery current iscontinuously supplied through resistance 46, contacts 43 and3lyoperating winding of meter '70 and resistance 74 to ground;resistance '75 forms a shunt path to ground for the meter. The meterdeilects to marking. .Battery current through resistance 45 and contact43 is also supplied to the v'armatureV 64. When the armature actuallyengages either Contact S 0r M equalV potentials will be applied to Vbothterminals of the meter, and the meter Vneedle will remain onzero.'Immediately after the ar- The armature vibrating in accor mature breakscontact, current willagain ow through the meter winding since thebattery is continuously connected to-meter terminal 73 and the meterneedle will then be deected toward the marking side. f Y

With the armature oscillating at a frequency corresponding to thealternating current source 80, the interruptions ofthe battery current4at the contacts S and M will control the degree of deflection oi theneedle.

For minimum requirements `of contactv euciency a standard deilectionV`on the meter is prescribed vfor the test. That delectionis small whenthe contacts are clean, and isV occasioned by substantially no currentilowing through the meter, a larger deflection of the meter indicatingpoor contact or poor connections to .the

contact members. By this provision, fluctuation in the voltage of thelocal current source need notV be taken into consideration in thereadings or be safeguarded against. Y

If, after cleaning the contacts a repetition of the test reveals anunsatisfactory condition by a deflection of the meterneedle greater thanthe acceptable maximum deflection, other defects may be the cause, suchas, unsymmetrical adjustment of the contacts with respect to thearmature or a loose connection in the wiring to the relay.

The successful removal of such defects may be observed by repeating thistest.

Bias test The bias test is for the purpose of facilitating adjustment ofthe pole pieces to eliminate bias.

The effective circuit for this test is shown in Fig. 4. Key is closedand key 30 isoperated to the right or bias side.

In this circuit the relay windings are connected to the alternatingcurrent source 80 over a path traced through resistances 81 and' 82 andspring contacts 35 and 36. Current is supplied to the armature throughresistance 46. and con'- tact 43.

The armature vibrating in accordance with the frequency of thealternating .current source 80 will oscillate between the marking andspacing contacts, and the meter needle will deflect alter-v nately toright and left forming an image before the scale.

Assuming that the-,pole pieces have been given their preliminaryadjustment and that the-contacts havebeen made` eflicient as observed'bythe tests already described there may still be a lack of symmetry in thepole adjustment and in the contact conditions which would be the causeof an undesirable bias. This bias is apparent from an unsymmetricaldisposition of the needle image with respect to zero in the meter, andmay be compensated for, irrespective of its cause by adjustment of bothpole pieces until the imageV becomes centered on the meter scale.

"Relay position the circuit continuing through therelay windingsinseries over another group of key contacts to ground. Under theconditions shown in Fig. 5, key 20 is operated to the leftor markingside and the armature would swing Vto the M contact. Current is thensupplied via resistance 46, contact 43 to the armature 64, thence Y,over contact 3l to the winding of meter '70 causing the meter needle todeect to the marking side. By reversing key 20 to the right or spacingYposition a reversal of current inthe relay windings may beeffe'ctedwherebyV theY armature is `operated to spacing position whichin -turn is indicated on the meter.

Key 20, normally open, isl

What is claimed is: l

t l. A, relay testing apparatusl comprising a meter, a source `ofcurrent, contact means for insertion of a relay having an operatingwinding and contacts in circuit with said meter and source, andswitching means to enable `alternative circuit conditions to be set upwhereby tests may be successively made for bias adjustmentl and contactefficiency respectively of said relay.

2. A circuit for testing relays comprising an indicating device, aWinding for said device, a

source of direct current, a resistance connected,

in shunt of said winding, the center point of said resistance beingconnected to one pole of said direct current source, -a connecting blockassociated vwith -said circuit having apertures for receiving the prongsof the relay to be tested, periodic current means for vibrating therelay to be testecLand circuit means for causing a flow of currentthrough the Winding of said indicating device with a consequent visibleindication on said device whenever the armature and contacts of therelay being vibrated touch one another and at no other time.

3. A 'circuit for testing the contact eiiiciency of relays comprisinganfindicating device, a winding for said device, a source of directcurrent, a resistance connected in shunt of said winding, a

`point intermediate Athe terminals of said resistance being connected toone pole of saidv direct current source, a connecting block associatedwith said circuit having apertures for relceiving the prongs of'therelays to`be tested,

periodic current means for Vibrating the relay to be tested,`and circuitmeans for causing a'flow of current through the winding of saidindicating device Vwith a consequent visible indication on saiddevice'whenever the .contacts of the relay being vibrated do not touchone another or make. poor contact due to troubles such as dirty ordefectivejcontacts, poor adjustmentA and the like. v v

` 4. A measuring circuit for testinga vibrating y relay having anarmature alternately touching opposite contacts of the relay comprisinga sensitive indicating device having an actuating winding with twoterminals, a source of current, aY

resistancegconnected in shunt of the winding of said indicating device,a point intermediate the lterminals of said resistance kbeing connectedto one pole of said source of current, a conductor y forA connecting thearmature of said relay to the other pole of said source of current andleads for separately connectingthe terminals of the Winding` of saidindicating device to said oppo-v site contacts.

5. A circuit for testing relays having an arma` ture and a pair ofcontact members, comprising a meter Ahaving a winding, with twoterminals, a

direct current source, a symmetrical connection from said winding tosaid source, a directr circuit connection from said source to oneterminal'of said meter-,Va direct circuit connection from said sourcethrough the 'armature and alternate contacts of said relay to the otherterminal of said meter to produce a zero current condition in said meterwinding, and an alternating current source connected to the relaywinding to supply cur-V rent to oscillate said armature'between saidalternate contacts atrthe frequency of said alternating current todisturb the zero current condition in said meter-windingY in accordancewith the contacting condition between said armature and y saidalternatecontacts. y A ANDREW D. DowD.

